It is known that properties of plastics such as heat insulation, sound absorption, buoyancy, elasticity and weight reduction are improved by mechanically foaming plastics, involving foaming by using reactive gas or foaming by using foaming agents. Such foamed plastics are widely used as soundproof material, heat insulators, building material, lightweight structural material, packaging material, insulating material, cushion material, quakeproof material, footwear, automobile interiors, and other articles. Many usable resins are known, and various foaming techniques are also known.
To save energy, resources and space, it is desirable to improve heat insulation and soundproof performance with a material that is as thin as possible.
However, in the prior art, it has proved very difficult to reduce the thickness of formed resins. The heat insulation or soundproof performance of foamed resins decrease in proportion to a reduction in their thickness.